I am running for the U.S. Senate from the Great State of Arizona, for one unwavering reason: to support the agenda and policies of President Donald Trump in his mission to Make America Great Again. https://t.co/ANppBdDOtp

Mr Arpaio served as the elected sheriff of Maricopa County, Arizona for 24 years until he lost the seat to a Democrat in 2016.

He rose to national prominence for detaining Spanish-speakers under suspicion of being undocumented migrants and for his sweeps of Hispanic communities searching for undocumented immigrants.

The former sheriff was convicted in July of deliberately violating a 2011 injunction halting his practice of detaining migrants who are not suspected of having committed a state crime. Only federal officers have jurisdiction over immigration.

In his interview with the Washington Examiner, Mr Arpaio proposed plans to deal with undocumented immigrants who came to the US as children.

"I have a far-out plan, which may look stupid," he said. "When they come to your attention that they're here illegally, these young people, deport them back to Mexico - or whatever - and then try to put them on a fast track to come back into the United States legally with special permits."

Mr Arpaio said immigrants should be proud of where they come from and that, "everybody would be happy, you deport them and then let them come back with all their education here".

He outlined several of his priorities and reasons for running in a fundraising memo to supporters.

Among them include combating the "liberal Left" and their attacks against gun owners and "unborn children".

Image copyrightGetty ImagesImage caption
Arpaio was known for his anti-immigration stance, and tough enforcement tactics

He also said the country was no longer recognisable now that "millionaire athletes are lionized by fake news media as 'heroes' for disrespecting the American flag and refusing to stand for our national anthem".

Several Democratic lawmakers have been outspoken on Twitter about Mr Arpaio's decision to run.

Some are warning that in such a politically competitive state, Mr Arpaio's bid could fuel Democrats to organise with more force as they did in December's Alabama race, where Democrat Doug Jones beat Republican candidate Roy Moore.

BREAKING: Joe Arpaio is running for senate in AZ. Didn’t we just prove in Alabama that a racist and person of poor moral character should not be elected to the United States Senate? https://t.co/kc0iNDgByh